1. Field of the Invention
The present invention relates to a technology for retracting a head on a storage medium by detecting a fall of a storage device, with a capability of preventing a degradation of performance due to an erroneous detection of the fall.
2. Description of the Related Art
A magnetic disk drive is mainly used as an auxiliary storage device of a general-purpose computer and for a business-purpose device that requires high-capacity random access data recording. Furthermore, use of the magnetic disk drive as a general household appliance has increased recently, with an advance of digitalization of household appliances and an increase of applications to record data such as audio-visual data as digital data (for example, a hard disk video recorder and a portable music reproducing device).
However, when the magnetic disk drive receives a strong impact due to a fall, a head collides with a disk surface and the disk surface gets scratched, and data reading and writing may become impossible. Particularly, falls of the magnetic disk drive while it is in operation cause the magnetic disk drive to become easily out of order. Therefore, when handling a product that includes a magnetic disk drive for a portable application, an attention had to be paid to avoid giving a strong impact to the product.
Japanese Patent Application Laid-Open No. 2002-8336 discloses a technology that uses a fall sensor to prevent damages caused by falls of the magnetic disk drive and retracts the head from the disk surface when a free fall of the magnetic disk drive is detected.
However, the conventional technology had a problem of degrading the performance of the magnetic disk drive, because the conventional technology simply detects falls of the magnetic disk drive and forcibly retracts the head from the disk surface.
The performance might be degraded because, in some cases, the fall sensor of the conventional technology erroneously detected falls during normal use when the magnetic disk drive was not falling or while carrying the magnetic disk drive, and each time the head was retracted from the disk.
Therefore, preventing degradation of performance of the magnetic disk drive resulted from erroneous detections of falls is becoming a critical issue.